Head-mounted display (HMD) devices are wearable by a human subject (i.e., user) for the purpose of presenting graphical content to the user. This graphical content may take the form of augmented reality (AR) content, virtual reality content (VR), and/or non-aligned heads-up-display (HUD) content.
AR typically refers to machine-based augmentation of a person's sensory perception of a physical, real-world environment. Within the context of visual augmented reality, a person's view of the real-world environment is supplemented or otherwise altered by computer-generated graphical content to create the appearance that the graphical content is present within the real-world environment. Head-mounted display devices for AR often incorporate one or more see-through display panels upon which graphical content is displayed to the user, enabling the user to directly view both the real-world environment and the graphical content within a combined AR view. Other head-mounted display devices for AR may capture a live view of the real-world environment via an on-board camera, and present that live view via a graphical display along with computer-generated graphical content integrated with the live view.
Virtual reality typically refers to machine-based replacement of a person's sensory perception with computer-generated content. Head-mounted display devices for visual VR may fully occlude the user's field of view with one or more graphical display devices upon which graphical content is presented to provide the user with a VR view. VR may seek to fully separate the user from the real-world environment in contrast to head-mounted displays that provide a live or direct view of the real-world environment.
Non-aligned HUD content refers to graphical content that is presented on a see-through display panel. While in general, HUD content may include AR content, non-aligned HUD content is not visually aligned with the user's field of view within the real-world environment. Hence, in contrast to more specific forms of AR content, non-aligned HUD content includes graphical content that is not necessarily presented in a manner that creates the appearance of the graphical content being present within the real-world environment. Non-aligned HUD content may take the form of human-readable information that provides the user with contextual information, for example.